Middle French or Medieval Latin; Middle French valide, from Medieval Latin validus, from Latin, strong, potent, from valēre


  • 1 : having legal efficacy or force; especially : executed with the proper legal authority and formalities <a valid contract>
  • 2 a : well-grounded or justifiable : being at once relevant and meaningful <a valid theory>
b : logically correct <a valid argument> <valid inference>
  • 3 : appropriate to the end in view : effective <every craft has its own valid methods>
  • 4 of a taxon : conforming to accepted principles of sound biological classification


sound, cogent, convincing, telling mean having such force as to compel serious attention and usually acceptance. valid implies being supported by objective truth or generally accepted authority <a valid reason for being absent>


The term validity in logic (also logical validity) is largely synonymous with logical truth, however the term is used in different contexts. Validity is a property of formulas, statements and arguments. A logically valid argument is one where the conclusion follows from the premises. An invalid argument is where the conclusion does not follow from the premises. A deductive argument may be valid but not sound. In other words, validity is a necessary condition for truth of a deductive syllogism but is not a sufficient condition.